Arc extinguishing chambers



M ch 5, 1963 K. H. DATE 3,080,467

ARC EXTINGUISHING CHAMBERS Filed Jan'. 20, 1960 2 Sheets-Sheet 1 Hill, 19

5: f; 4! Mn ml iil ://///1 March 5, 1963 K. H. DATE ARC EXTINGUISHING CHAMBERS Filed Jan. 20, 1960 2 Sheets-Sheet 2 mu lw l l ub ldv INVENTOR. Razz/0 iz ervy Date BY adm t flttor'm United States Patent This invention rel .tes to circuit interrupters or is liquid immersed type and more particularly to are extinguishing chambers for such circuit interrupters.

An object of this invention is to provide a new and improved arc extinguishing chamber for interrupting both high and low magnitude overcurrents.

Another object of the invention is to provide an arc extinguishing chamber wi h vents which provide adequate pressure relief area but do not permit elongation of the arc.

- It is a further object of the invention to provide an arc extinguishing chamber in which the are core is vented through a plurality of long narrow interconnected slots to provide a maximum of exhaust velocity.

A still further object of the invention is to provide a novel means for indexing the insulating plates used to form are extinguishing chambers.

These and other objects and advantages of the invention will become more apparent from the detailed description of the invention taken in view of the accompanying drawings in which:

FIG. 1 is an elevational view, partly in section, of an interrupting chamber according to the instant invention;

' FIG. 2 is a view taken along lines 2-2 of FIG. 1;

7 FIG. 3 is a sectional view taken along lines 3- of FIG. 1; and

"FIG. 4 is an exploded perspective view showing the individual plates which comprise the interrupting chantber and the arrangement thereof; and

FIG. 5 is a view taken along lines 5-5 of FIG. 4.

In general terms, the invention comprises an arc-extinguishing unit for a circuit interrupter of the liquid dielectric type having a longitudinal bore and a plurality of elongate venting passages extending la orally therefrom, said passages being characterized by substantially linear sidewalls and whose widths are several times larger than their height, whereby appreciable venting area is provided without aflo-rding sui'licient height in the direction parallel to said bore to permit the to elongate through said vents. In addition, the length of the venting passages is preferably several times larger than its Width so that the products of arcing will be relieved at a high velocity.

The are extinguishing chamber may comprise, according to a more specific aspect of the invention, a plurality of contiguously disposed insulating plates forming a stack and having a longitudinal bore for confining the are over a substantial portion of its length. Spaced apart ones or" said plates are provided with an elongate venting slot cut longitudinally through one end while the "remaining plates have imperforate surfaces adjacent said venting slot to form therewith a plurality of elongate venting passages extending laterally of said bore.

According to a further aspect of the invention, a pressure chamber is disposed below the interrupting unit and in communication therewith wherein the movable contact, which draws the arc, resides in said pressure chamber when it is in its fully opened position.

Referring no r to the drawings in greater detail FIG. 1 shows the novel are extinguishing chamber according to the instant invention which is designated by the general reference numeral i l and which is adapted for use in an oil immersed circuit interrupter such as the one described in Patent No. 2,692,925 issued to C. Schindler on Gctoice her 26, 1954 and assigned to the instant .i'sslgnee. It will be understood that the arc extinguishing chamber is immersed entirely beneath the circuit interrupters dielectric oil.

The extinguishing chamber it; comprises a cylindrical tube 11 composed of any suitable insulating material, such as moulded resin, and in which a high current portion 12 and a low current portion 314 are arranged coaxially near its lower end. A stationary contact 16 is disposed in tube ll above the high current portion 12 and a movable contact rod 1%, engageable with fixed contact it, extends coaxially through arc extinguishing portions 12 and 1 5 and from the lower end of tube Ill. The are extinguishing chamber iii is suitably mounted in the circuit breaker by means or" an insulating bracket member 1? and a transverse rnounting tube 2b. The current path through chamber ltl is from a conductive stud 21, which extends through the upper end of tube 11 and which is adapted to be connected to one of the circuit breakers terminals (not shown), to the fixed and movable contacts 16 and 18, and then through a conductive movable contact carrier arm 22, upon which the movable contact 18 is carried. In order to prevent tube 11 from becoming charred during an interrupting operation, a fibre arcing sleeve 24 is disposed on the inner surface thereof and around fixed contact 16.

Considering FIG. 4, it will be observed that the high current interrupting portion 12 is composed of a plurality of stacked, non-conducting fibrous plates. These include venting plates 3n? having elongate, longitudinally extending, Ushaped slots 32 cut in their front edges and reservoir plates 34 having longitudinally extending V -shaped slots cut in its rear edges. Upper and lower end plates 37 and 33, respectively, are disposed at each end of portion 12 and each has an aperture 39 for slidably receiving the movable contact 18.

Slots 32 and 36 are of suficient length so that their innermost portions dd and 41, respectively, overlap to form a continuous bore 43 through portion 12 and which is in register with the apertures 39 in end plates 3'? and 38. Also, because the length of plates and 3d exceeds the diameter of tube ll, as seen in FIGS. 1 and 4, a longitudinal opening 4-5 is provided in one side of tube 11 for receiving one side of the high current portion 12. In addition, because the length of slots 32 is greater than the length of slots 35, bore 43 is substantially coaxial with tube 1% and movable contact 18.

The fibrous plates or" portion 12 are so arranged that .s of reservoir plates 34 separate each of the venting ates 3% except the lowermost two which are separated single reservoir plate 3 t. in addition, the upper the upper and lower end plates 37 and 38 respectively. This arrangement provides a plurality of laterally extending vents 44 formed by slots 32 and the surfaces of plates 3-!- and which connect one side of bore 43 to the exterior of the chamber 1%. it can also be seen from i l-G. 1 that the thickness of each venting plate 30 is substantially s iraller than the width of slots 32 and approximately one-half the thickness of the reservoir plates as so that the height of vents 4, in the axial direction, is much smaller than their width and the spacing between the adjacent vents. By proportioning the cross section of venting passages in this manner, a relatively large total venting area can be attained while the slot height is maintained at a minimum. This provides suf iicient venting area to adequately relieve the gaseous products of arcing while at the same time preventing the elongation of the are by its displacement into said vents. In addition, the length of slots plus the distcance between them also helps to confine the arc in the ore 43.

The reservoir plates 34 are so arranged that slots 35 extend from bore 43 toward the rear of tube It to pro vide a plurality of oil reservoirs 46 on the opposite side of bore ,3 relative to vents 44. These reservoirs are defined by slots 36, the surfaces of plates 30 and the inner surface of tube Ill.

With reference to FIGS. 1, 3 and 4, it can be seen that the high current portion 12 is mounted in tube 11 by a groove d formed on the interior thereofopposite opening 45, and having substantially the same width, for receiving the inner ends of plates and 34. In addition, an apertured stop plate 54 is disposed in the end of transverse mounting tube 29 and held in abutment with the upper and lower end plates 37 and 38 by a metallic retaining ring 56 which is disposed in a suitably formed groove Sid-on the interior of tube 20. The outer end of each of the plates 30 and 34 is reduced to form a shoulder 59 for abutment with the edges of the apertures in stop plate 54.

The low current interrupting portion 14- comprises a substantially closed cylindrical chamber located below portion 12 and separated therefrom by a fiber disc 60. Portion 14 is defined by a disc 64?, a fiber sleeve 61 disposed on the inner surface of tube 11, and at its lower margin by a second fiber disc 61. Discs 6t) and 62 each have a coaxial aperture 63 for. slidably receiving movable contact 13. Portion 14 is aiiixed in the tube lid by a retaining ring dddisposed below it in a suitably formed groove 65 at the lower end of tube it During the interruption of a large fault current, movable contact 18 is moved out of engagement with fixed contact 16, drawing an arc therebetween. The high energy of the arc decomposes the dielectric fiuid in bore 43 and the adjacent fluid in reservoirs 46, to produce ionized gases and vapor. As a result, the pressure within portion 12 rises rapidly, and when it reaches a predetermined value, it is relieved through slots 44 at an extremely high velocity. The height of slots 44 is kept at an extremely small value to insure that the arc is not lengthened as the hot gases are relieved. This is extremely important because are energy is a function of arc length as well as are voltage, are current and duration. On the other hand, the width of slots 44 is made relatively large to provide sufiicient venting area so that the internal pressure does not rupture tube 11.

In addition, the length of the slots are sufiiciently long to insure that the gases are exhausted at an extremely high velocity. This causes these gases to vaporize and cool as they travel down the slot, thereby cooling the are core and removing electrons and ions necessary for the arc to restrike after the alternating current passes through zero. This high velocity is aided by making the sidewalls of vents 44 substantially parallel. Also, making the sidewalls parallel reduces the possibility that erosion or" the plates during arc interruption will appreciably change i the area of the opening. It can be seen, therefor, that the configuration of slots 44 plays an important role in the dissipation of are energy so that the arc will be extinguished. Efficient results have been obtained where the ratio of slot width to height is approximately six to one and the ratio of length to width is approximately three to one.

When the device is called upon to interrupt a relatively low current overload, the pressure developed in portion 12 is not sufficient to deionize the are core prior to the time that the end of movable contact 13 reaches its fully opened position, wherein its upper end is disposed within' chamber 55. However, when the movable contact 18 reaches this position, a long dielectric gap is provided between it and stationary contact 16. In addi- 7 tion, as the dielectric fluid vaporizes in chamber 55, the

pressure will build up to a point where it will discharge rapidly out of the lower ones of vents 44, thereby eifectively deionizing the arc in the manner discussed with respect to a high current fault. For this reason the low ermost vents 44, through which most of these gases dis charge, are disposed closer together than the remainder. As seen in FIG. 5, the plates which form the high cur-- rent portion 12 are indexed by means of a pair of embossed areas 70 and 71 which are formed at suitable locations on each. In this manner, the plates can be stacked without the necessity for pins or rods utilized in prior art devices. In the illustrated embodiment, these areas are formed by partially stamping a pair of small cylindrical sections from each plate so that the protruding portions of one plate will be received into the recessed portion of the plate immediately below it.

While only a single embodiment of the invention has been shown and described, other modifications will be suggested once the inventive concept is known. Accordingly, it is intended to cover in the appended claims all modifications that fall within the true spirit of the invention.

I claim: I 1. In a circuit breaker of the oil-immersed type, an arc extinguishing unit, fixed and movable contact means for establishing an are within said unit, said unit including a substantially enclosed pressure chamber spaced from said stationary contact means, a plurality of contiguously disposed insulating plates forming a stack, said staclr being disposed between said stationary contact means-and said pressure chamber and defining a substantially enclosed arc chamber havinga longitudinal bore for confining the are over a substantial portion of its length, spaced apart ones of said plates having U-shaped, elongate venting,

slots cut in one end thereof and intersecting said bore, said spaced apart ones of said plates also having an im perforate portion extending from the oppositeside of said bore, the opposite sides of said slots being substantially parallel, the remaining plates in said stack having imperforate surfaces adjacent said venting slots to form therewith a plurality of elongate venting passages extending laterally of said bore for interconnecting it with the exterior of said unit, said remaining plates being perforate on the opposite side of said bore for providing a plurality of oil reservoirs, the widths of said slots being substantially smaller than their lengths and several times larger than the thickness of said venting plates, whereby appreciable venting area is provided while the dimension of said passages in the direction parallel to said bore is limited, one of said plates defining the margin between said pressure chamber and said are chamber and being substantially imperforate except for an opening in register with said bore for communicating with said vents, those venting passages immediately adjacent said pressure chamber being more closely spaced to each other than those venting passages more remote from said pressure chamber, the end ofsaid movable contact residing in said pressure chamber when the same is in its fully opened position.

2. In a circuit breaker of the oil immersed type, an arc-extinguishing unit, means including a movable con tact for establishing an are within said unit, said unit including a plurality of contiguously disposed insulating plates forming a stack for defining a substantially enclosed arc chamber, said plates having perforations which provide a longitudinal bore for confining the arc for a substantial portion of its length, spaced apart ones of said plates having U-shaped, elongate venting slots cut in one end thereof and intersecting said perforations, the opposite sides of said slots being substantially parallel, those plates between said spaced-apart plates having imperforate surfaces adjacent said venting slots to form therewith a plurality of elongate venting passages extending laterally of said bore for interconnecting it with the exterior of said unit, the widths of said slots being substantially smaller than their length and several times larger than the thickness of said venting plates whereby appreciable venting area is provided while limiting the dimension of said passages in the direction parallel to said bore, said unit including a pressure-chamber disposed below said plates and having an opening in register with said bore for communication with said vents, the end of said movable contact residing within said pressure chamber when the same is in its fully opened position, those venting passages adjacent said pressure chamber having a closer spacing than those passages more remote therefrom, said pressure chamber having a pair of axial openings for receiving said movable contact and being otherwise imperforate.

3. The device set forth in claim 2 wherein each of said plates having a plurality of embossed portions providing an elevation on one surface of the plate and a depression on the other surface thereof, the elevation on each of said plates being in register with the depression on the adjacent plate whereby said plates may be indexed without the use of additional members.

References Cited in the file of this patent UNITED STATES PATENTS Whitney et a1 Nov. 20, 1934 Leeds Feb. 18, 1947 Leeds Nov. 15, 1949 Umphrey Aug. 4, 1953 Salzer Aug. 2, 1955 Balentine Sept. 6, 1955 Pease Feb. 17, 1959 FOREIGN PATENTS Sweden Nov. 7, 1933 Great Britain Jan. 17, 1941 France May 6, 1957 

1. IN A CIRCUIT BREAKER OF THE OIL-IMMERSED TYPE, AN ARC EXTINGUISHING UNIT, FIXED AND MOVABLE CONTACT MEANS FOR ESTABLISHING AN ARC WITHIN SAID UNIT, SAID UNIT INCLUDING A SUBSTANTIALLY ENCLOSED PRESSURE CHAMBER SPACED FROM SAID STATIONARY CONTACT MEANS, A PLURALITY OF CONTIGUOUSLY DISPOSED INSULATING PLATES FORMING A STACK, SAID STACK BEING DISPOSED BETWEEN SAID STATIONARY CONTACT MEANS AND SAID PRESSURE CHAMBER AND DEFINING A SUBSTANTIALLY ENCLOSED ARC CHAMBER HAVING A LONGITUDINAL BORE FOR CONFINING THE ARC OVER A SUBSTANTIAL PORTION OF ITS LENGTH, SPACED APART ONES OF SAID PLATES HAVING U-SHAPED, ELONGATE VENTING SLOTS CUT IN ONE END THEREOF AND INTERSECTING SAID BORE, SAID SPACED APART ONES OF SAID PLATES ALSO HAVING AN IMPERFORATE PORTION EXTENDING FROM THE OPPOSITE SIDE OF SAID BORE, THE OPPOSITE SIDES OF SAID SLOTS BEING SUBSTANTIALLY PARALLEL, THE REMAINING PLATES IN SAID STACK HAVING IMPERFORATE SURFACES ADJACENT SAID VENTING SLOTS TO FORM THEREWITH A PLURALITY OF ELONGATE VENTING PASSAGES EXTENDING LATERALLY OF SAID BORE FOR INTERCONNECTING IT WITH THE EXTERIOR OF SAID UNIT, SAID REMAINING PLATES BEING PERFORATE ON THE OPPOSITE SIDE OF SAID BORE FOR PROVIDING A PLURALITY OF OIL RESERVOIRS, THE WIDTHS OF SAID SLOTS BEING SUBSTANTIALLY 